Apparatus including power unit for



Jan. 25, 1949. E. A. ROCKWELL 23,031

APPARATUS INCLUDING POWER UNIT FQR SETTING BRAKES Original Filed Sept.1, 1943 INVENTOR t pw/a/PoAfiozru/czl.

ATTORNEY Reissuecl Jan. 25, 1949 APPARATUS INCLUDING POWER UNIT FORSETTING BRAKES Edward A. Rockwell, Shaker Heights, Ohio, as-

signor to Eleetroiio Corporation, Cleveland, Ohio, a corporation ofDelaware Original No. 2,423,204, dated July 1. 1947, Serial No. 501,034,September 1, 1943. Application for reissue June 24,

My invention relates particularly to a brake operating mechanism andwhich is applicable to the operation of brakes generally, for example inthe operation 01 automotive vehicles, automobiles, etc.

The object of my invention is to provide a brake operating mechanismwhich is efilcient in operation and by means of which a short range oftravel of the actuating device, as for instance a pedal or treadle, canbe obtained. Another object of my invention is to provide means wherebythe brakes may be movedinto operative position by a hydraulicallycontrolled source 01' power and in which the main braking effect may beattained manually. Another object is to move the brakes into operativeposition by power stored from a spring device, after which the brakingeffect may be attained manually by a short range of pedal travel. Onepurpose of this device is to provide a simple cheap power unit that canbe applied to passenger cars so as to make available a treadle controlinstead of a long range pedal, thereby saving considerable room in thefront compartment of the automobile. It is the purpose of this device toaccomplish this short range pedal operation with a very cheap and simplevacuum power device. In this invention the power device is in the natureof an initial spring-actuated slack adjuster, the vacuum being used toreturn the spring which has previously set the brakes so that the brakeswill be completely released normally in the operation of the vehicle. Inshortening the range of the pedal travel the manual work has beenreduced, but normal pedal pressures are available. This arrangementenables effective brake operation to be obtained even when the vacuum isnot available, as for instance in engine stalling on a steep gradeorwhen the vehicle is being towed.

Another object is to provide a mechanism whereby the shifting from thepower application for setting the brakes to the manual operation forapplying the brakes is obtained by a double check valve preventing thefeed back of the manual pressures to the power means for setting thebrakes, the double check valve being controlled by the pressure in thesystem. A further object is to enable the brakes to be applied in thisway by a relatively small master cylinder. In the arrangement inaccordance with my invention, the master cylinder is smaller in diameterso that the overall ratio will be the same as in an ordinary passengercar brake system, even though the travel has been reduced, the travelonly being 1948, Serial No. 34,957

31 Claims. (Cl. 188-152) reduced, however, by reason of the slack beingtaken up by the power unit for setting the brakes. The spring, whichsets the brakes, is preferably just about sufllcient to take up theslack as the brakes wear, and during a condition of towing the vehicleor manipulating on a grade, as mentioned before, the brakes might dragslightly but would be under complete control of the operator withoutexcess pressures. When the vacuum is on, the only function the vacuumhas is to assure the release of the brake shoes so that the brake willnot drag.

Further objects of my invention will appear from the detaileddescription of the same hereinafter.

While my invention is capable of embodiment in many different forms, forthe purpose of illustration I have shown only one form thereof in theaccompanying drawing in which the figure is a diagrammaticrepresentation, partly in section, of an apparatus made in accordancewith my invention.

In the drawing, I have shown a treadle i carried by a pivot 2 on afloor-board l 01' an automobile. The upper end of the treadle I has apivot 4 connecting it to a link 5 which has a pivotal connection 8 to anangular lever I carried by a fixed pivot I on the automobile chassis.The lower end of the lever i has a pivotal connection 9 to a push rodll. one end of which is received in a recess H in a piston ii of arelatively small master cylinder is of any desired construction,provided with the usual liquid reservoir ll hav ing a filling opening iswith a vented cap l8 thereon. A recuperating passage or port ll connectsthe reservoir II to a chamber it in the master cylinder ii, in theretracted position of the piston II, which is connected by a pipe Is toa cylinder 20 having a valve operating plunger 2i, having a seal Zia,therein provided with a stem 22 connecting it to a valve 23 having onthe upper face' thereof a pin valve 24 adapted to seat on a valve seat25 in an air vent 28 located on a valve chamber 21. A spring 28 in thechamber 21 normally forces the valve}; against a valve seat 29 withinsaid chamber 21 so as to normally open the valve 24, 25. A pipe 30connects the side of the valve chamber 21 with a lower diaphragm casing3i provided with a flexible diaphragm 32. which is clamped between thelower diaphragm and an upper diaphragm casing 33,'connected by a pipe 3to a vacuum inlet pipe 35, which is connected to the engine manifold ofthe automobile or any other desired source of vacuum. In the ss,osi

3 pipe there is a check valve I! normally pressed against a valve seat81 by memo! a spring II located in the pipe 35 and abutting against ashoulder as therein. A screw coupling connects the pipe I4 with the pipe35. The said pipe 34 is connected at its lower end to a chamber 4iadapted to communicate with the valve casing 21 when the valve 23 is inopen position. Within the upper diaphragm casing 33 there is a spring 42which acts as an accumulator and is sumciently strong to overcome thebrake-shoe retracting springs hereinafter referred to. The spring 42 issupported at its upper end against the interior of the upper diaphragmcasing 33 and at its ower end by a flared disk 43 supported by the(118111.88111 32, on the under-face or which there is a similar flareddisk 44. The two disks 43 and 44 are secured by a screw 45 to a hollowplunger 46, provided with a seal "a, having a cylindrical chamber 41therein to receive a head 48 of a lost motion valve operating rod 4!which passes through an opening II in the lower end of the plunger 46.The rod 48 passes downwardly through a cylinder Si, in which the piston48 reciprocates, and thence through a passageway 52 to a double checkvalve chamber 53, where it is connected to a double check valve 54. Thevalve 54, in its upper position, presses against a valve seat 55 and inits lower position against a valve seat 68. The side 01 the valvechamber 63 is, furthermore, connected by a pipe 51 to a branch pipe 58leading to front wheel brake operating cylinders 50 and i4 and by abranch pipe ii to rear wheel brake operating cylinders 82 and 83. Eachof the cylinders 5!, I, 62 and i3 is arranged to operate a pair of brakeshoes 44 and 65 in the usual way, carried by pivots B6 and i1, and whichhave a retracting spring I connected between the brake shoes 64 and 35,such as are carried by each of the wheels of the automobile. The lowerend of the valve casing 53 is connected by a pipe 89 to the lower end ofthe cylinder 20.

In the operation of my invention, when the automobile is in operation, avacuum will be supplied from the engine manifold through the pipe 35, byunseating the check valve 36, so as to supply the vacuum to the upperdiaphragm chamber 33, thus storing up power in the accumulator spring 42due to the air pressure received from the atmosphere through the vent 28and pipe 30 on the under-face of the diaphragm 32. When it is desired,in the driving oi the automobile, to apply the brakes the treadle l ismoved downwardly so as to move the master cylinder piston I! to theright, thus applying a very slight amount of pressure to the under-faceof the piston 2i suihcient to unseat the valve 23, 29 which is backed bythe very light spring 28. This has the immediate result of closing thevent 26 and admitting vacuum from the pipe 34 through the pipe 30 to thelower diaphragm casing 3|, thus balancing the pressures on the oppositesides of the diaphragm 32. The stored up power in the accumulator spring42, thereupon, immediately moves the plunger 46 downwardly, thusapplying a hydraulic pressure from the spring 42 through the pipe 51 tothe brake cylinders 58, 60, B2 and 68 so as to seat the double checkvalve 54 on its valve seat 56 and overcome the retracting springs 68 onthe four wheels of the automobile and so as to move the brake shoes 84and 85 thereon into contact with the brake drums in the usual way. Uponthe increase of pressure manually from the treadle I, thereafter, thedouble check valve I4 is moved upwardly so as, to seat against its uppervalve seat I after being unseated from the valve seat 88 which isinsured by the lost motion connection with the valve operating rod 48,so as to prevent the manual pressure from being applied to the powermeans and thus applying the manual pressure for producing the brakingeffect through the wheel cylinders 50, 80, 62 and 63. By this meanssumcient braking effect is obtained on the wheel brakes by the manualpressure, without the necessity of moving the treadle I through morethan a very short range of travel. For this reason, also, it will beseen that the master cylinder H can be made of comparatively smalldimensions. Upon the releasing movement of the treadie I the manualpressure is released from the brakes through the pipes 89 and IS, theliquid being returned thereby to the master cylinder i3 and thence iorequalization through the port H to the reservoir 14. When the manualpressure has been fully released the valve plunger 2I will movedownwardly under the influence of the light spring 28 so as to seat thevalve 23 on the seat 28 while at the same time opening the air ventthrough the valve 24, 25. The atmospheric air thus admitted through thepipe 30 will enter the lower diaphragm casing 3| so as to compress thespring 42 and store up energy therein for the subsequent setting of thebrakes when the latter are desired to be operated again. In other words,the double check valve 54 becomes again seated against its valve seat 56whereupon the brakes can be set by the movement of the plunger 46 due tothe expansion of the spring 42 and it is only thereafter that the doublecheck valve 54 is moved oil its seat 58 to apply the manual pressure toproduce the braking effect on the wheel brakes of the automobile. Inthis way a very compact simple and efiicient brake-operating mechanismis attained which is efi'ective under the different operating conditionsor the automobile, while at the same time utilizing only a very smallmaster cylinder and operating the same with a very short pedal travel.The short pedal travel is very much desired, as it provides a bettercontrol at the brakes and does not require any substantial movement ofthe treadle to apply the manual force of the brakes during the settingthereof.

While I have described my invention above in detail I wish it to beunderstood that many changes may be made therein without departing fromthe spirit of the same.

I claim:

1. In a device of the character described, a source oi power, a wheelbrake, manually operable means including a master cylinder having apiston provided with a seal, apparatus adapted to apply said powerto'substantialiy merely set the brake hydraulically, and means,including a double check valve, connecting the master cylinder with saidapparatus so as to thereafter apply a manual hydraulic pressure on saidwheel brake and to out 01f the application of the power upon the brakewhile the manual pressure is being applied and allow the return 01 theliquid through the double check valve to the master cylinder.

2. In a device of the character described, a

source of vacuum, a vacuum motor operated thereby, a vacuum valveassociated therewith, a wheel brake, manual operating means having ahydraulic connection to operate said valve, apparatus including a springadapted to apply said vacuum to release spring pressure while the vacuumis being applied to set the brake, and means connecting the manual meanswith said apparatus so as to thereafter apply merely a manual pressureon said wheel brake after the release of the vacuum.

3. In a device of the character described, a source of vacuum, a vacuummotor-including an accumulator spring operated thereby, a wheel brake,manual hydraulically operating means including a master cylinder havinga piston provided with a seal, apparatus, including a pressure-applyingplunger and cylinder and a liquid cut-off valve, adapted to apply thepressure of said spring to the brake to set the brake, and meansconnecting the master cylinder with said apparatus so as to thereafterapply a manual pressure, while cutting off the liquid from the springpressure by the cut-oil valve, on said wheel brake.

4. In a device of the character described, a source of vacuum, a vacuummotor including an accumulator spring operated thereby, a wheel brake,manual hydraulically operating means including a master cylinder havinga piston provlded with a seal, apparatus, including a pressure-applyingplunger and cylinder and a liquid cut-oil valve, adapted to apply thepressure of said spring to the brake to set the brake, and meansconnecting the master cylinder with said apparatus so as to thereafterapply a manual pressure, whilecutting ofi the liquid from the springpressure by the cut-off valve, on said wheel brake, said wheel brakehaving a retracting spring adapted to be overcome by the accumulatorspring.

5. In a device of the character described, a source of vacuum, a vacuummotor operated thereby, a wheel brake, manual hydraulically operatingmeans, a spring compressed by said vacuum, apparatus, including a,pressure-applying plunger and a liquid cut-oil valve, adapted to applysaid vacuum to set the brake by the force of said spring, and meansconnecting the man ual means with said apparatus so as to thereafterapply a. manual pressure, while cutting oi! the liquid from the springpressure by the cut-oi! valve, on said wheel brake, said vacuum motorcomprising a pressure-responsive diaphragm and said manual means havinga valve responsive to manual pressures for controlling the applicationof the vacuum to said diaphragm.

6. In a device of the character described, a source of vacuum, a vacuummotor including an accumulator spring operated thereby, a wheel brake,manual hydraulically operating means, a spring compressed by saidvacuum, apparatus, including a pressure-applying plunger and cylinderand a liquid cut-oil" valve, adapted to apply said vacuum to set thebrake by the force of said spring, and means connecting the manual meanswith said apparatus so as to thereafter apply a manual pressure, whilecutting oif the liquid from the spring pressure by the cut-off valve,from the manual means on said wheel brake, said vacuum motor comprisinga pressure-responsive diaphragm and said manualmeans having a valveresponsive to manual pressure for controlling the application of thevacuum to said diaphragm.

7. In a device of the character described, a source of vacuum, a vacuummotor including an accumulator spring operated thereby, a wheel brake,manual hydraulically operating means, apparatus, including apressure-applying plunger and cylinder and a liquid cut-oil valve,adapted to apply said vacuum to set the brake by the force of saidspring, and means connecting the manual means with said apparatus so asto thereafter apply a manual pressure, while cutting oi! the liquid fromthe spring pressur by the cut oil valve, from the manual means on saidwheel brake, said wheel brake having a retracting spring adapted to beovercome by the accumulator spring, said vacuum motor comprising apressure-responsive diaphragm and said manual means having a valveresponsive to manual pressures for controlling the application of thevacuum to said diaphragm,

8. In a device of the character described, a source of vacuum, a vacuummotor operated thereby, a wheel brake, manual hydraulically operatingmeans, a spring compressed by said vacuum apparatus adapted to applysaid vacuum to set the brake by the force of said spring, and meansconnecting the manual means with said apparatus so as to thereafterapply a manual pressure on said wheel brake, said vacuum motorcomprising a pressure-responsive diaphragm and said manual means havinga. valve responsive to manual pressures for controlling the applicationof the vacuum to said diaphragm and the said diaphragm having a plungerand a cylinder with a liquid cut-oil valve connecting it to the wheelbrake and cutting oil the spring pressure to the brake when the manuapressure is applied to the brake.

9. In a device of the character described, a source of vacuum, a vacuummotor including an accumulator spring operated thereby, a wheel brake,manual hydraulically operating means, ap-

paratus adapted to apply said vacuum to set the brake by the force ofsaid spring, and means connecting the manual means with said apparatusso as to thereafter apply a manual pressure on said wheel brake, saidvacuum motor comprising a pressure-responsive diaphragm and said manualmeans having a valve responsive to manual pressure for controlling theapplication of the vacuum to said diaphragm and the said diaphragmhaving a plunger and a cylinder with a liquid cut-off valve connectingit to the wheel brake and cutting ofl the spring pressure to the brakewhen the manual pressure is applied to the brake.

10. In a device of the character described, a source of vacuum, a vacuummotor including an accumulator spring operated thereby, a wheel brake,manual hydraulically operating means, apparatus adapted to apply saidvacuum to set the brake by the force of said spring, and meansconnecting the manual means with said apparatus 50 as to thereafterapply a manual pressure on said wheel brake, said wheel brake having aretracting spring adapted to be overcome by the accumulator spring, saidvacuum motor comprising a pressure-responsive diaphragm and said manualmeans having a valve responsive to manual pressures for controlling theapplication of the vacuum to said diaphragm and the said diaphragmhaving a plunger with a liquid cut-ofl' valve connecting it to the wheelbrake and cutting oi! the spring pressure to the brake when the manualpressure is applied to the brake.

11. In a device of the character described, a source of vacuum, a vacuummotor operated thereby, a wheel brake, manual hydraulically operatingmeans including a spring compressed by said vacuum, apparatus adapted toapply said vacuum to set the brake by the force of said spring, andmeans connecting the manual means caper with said apparatus so as tothereafter apply a manual pressure on said wheel brake, said manualapparatus having a valve responsive to man! ual pressures forcontrolling the application of the vacuum to said diaphragm and the saiddiaphragm having a plunger connecting it to the wheel brake, providedwith a double check valve adapted to alternately connect merely the saidspring pressure or the manual pressure with the wheel brake.

' 12. In a device of the character described, a source of vacuum, avacuum motor including an accumulator spring operated thereby, a wheelbrake, manual hydraulically operating means, apparatus adapted to applysaid vacuum to set the brake by the force of said spring, and meansconnecting the manual means with said apparatus so as to thereafterapply a manual pressure on said wheel brake, saidwacuum motor comprisinga pressure-responsive diaphragm and said manual apparatus having a valveresponsive to manual pressure for controlling the application pi thevacuum to said diaphragm and the said diaphragm having a plungerconnecting it to the whee-1 brake, provided with a double check valveadapted to alternately connect merely the said spring pressure or themanual ressure with the wheel brake.

13. In a device of the character described, a source of vacuum, a vacuummotor including an (0611311118170! spring operated thereby, a. wheelrake, manual hydraulically operating apparatus adapted to apply saidvacuum to set the brain: by the force of said spring, and meansconnecting the manual means with said apparatus so as to thereafterapply a manual pressure on said wheel brake, said wheel brake having aretracting spring adapted to be overcome by the accumulator spring,saidvacuum motor comprising a pressure-responsive diaphragm and saidmanual apparatus having a valve responsive to manual pressures forcontrolling the application of the vacuum to said diaphragm and the saiddiaphragm trolling the application of said power. a wheel brake,manually operable means including a master cylinder, a spring operableby the vacuum. apparatus connected to said valve and adapted, when thevacuum valve is moved to open position by hydraulic pressure from themaster cyinder, to apply said power to set the brake ressure from saidspring, and means connecting the manual means with said apparatus so asto thereafter apply merely a manual pressure on said wheel brake.

15. In a device of the character describe'i, a source of vacuum power, avacuum valve for controlling the application of said power, a wheelbrake, manually operable means including a master cylinder, a springoperable by the vacuum, apparatus connected to said valve and adapted.when the vacuum valve is moved to open position by hydraulic pressureirom the master cylinder, to apply said power to set the brake bypressure from said spring, and means connecting the manual means withsaid apparatus so as to thereafter apply merely a manual pressure onsaid wheel brake, said master cylinder being oi reduced capacity due tothe setting of the brake merely by the power from the power source.

16. In a device of the character described, a source of vacuum power, avacuum valve for controlling the application of said power, a wheelbrake, a spring operable by the vacuum, manuafly operable meansincluding a pedal having a short range of travel and a master cylinder,apparatus connected to said valve and adapted, when the vacuum valve ismoved to open position by hydraulic pressure from the master cylinder,to apply said ower to set the brake by pressure from said spring, andmeans connecting the manual means with said apparatus so as tothereafter apply merely a manual pressure on said wheel brake.

1'7. In a device of the character described, a source of vacuum power, avacuum valve for controlling the application of said power, a wheelbrake, a. spring operable by the vacuum, manually operable meansincluding a pedal having a short range of travel and a master cylinder,apparatus connected to said valve and adapted,

when the vacuum valve is moved to open posi- \tion by hydraulic pressurefrom the master cylinder, to apply said power to set the brake bypressure from said spring, and means connecting the manual means withsaid apparatus so as to thereafter apply merely a manual pressure onsaid wheel brake, said master cylinder being of reduced capacity due tothe setting of the brake merely by the power from the power source,

18. In a device of the character described, a source of vacuum, a vacuumvalve associated therewith, a wheel brake, manual operating means havinga hydraulic connection to operate said valve, apparatus, including a.spring and a movable wall associated with said spring, adapted to applysaid vacuum to release spring pressure while the vacuum is being appliedto both sides of said wall to set the brake, and means connecting themanual means with said apparatus so as to thereafter apply a manualpressure on said wheel brake.

19. In a device of the character described, a source of vacuum, a checkvalve to trap the vacuum received by the device therefrom, a vacuumvalve associated therewith, a wheel brake, manual operating means havinga hydraulic connection to operate said valve, apparatus, including aspring. adapted to apply said vacuum to release spring pressure whilethe vacuum trapped by said check valve is being applied to set thebrake, and means connecting the manual means with said apparatus so asto thereafter apply a manual pressure on said wheel brake andsubsequently release the pressure on the wheel brake by the trappedvacuum.

20. In a, device of the character described, a source of power, a wheelbrake, manually operable means including a master cylinder having apiston provided with a .seal, apparatus adapted to apply said power tosubstantially merely set the brakes hydraulically, and means, includinga double check valve, connectin the master cylinder with said apparatusso as to thereafter apply a manual hydraulic pressure on said wheelbrake and to cut oil the application of the power upon the brake whilethe manual pressure is being applied and allow the return of the liquidthrough the double check valve to the master cylinder, the check valvehaving a lost motion connection to the said apparatus so as to be movedthereby to open the check valve at one end of the lost motionconnection.

21. In a device of the character /described,-a source 01' vacuum, avacuum valve associated therewith. a wheel brake, manual operating 7means having a connection to operate said valve.

manual means with said apparatus so as to thereafter apply a manualpressure on said wheel brake.

22. In a device of the character described, a source of vacuum, a checkvalve to trap the vacuum received by the device therefrom, a vacuumvalve associated therewith, a wheel brake, manual operating means havinga connection to op erate said valve. apparatus including a spring,adapted to apply said vacuum to release spring pressure while the vacuumtrapped by said check valve is beingapplied to set the brake, and meansconnecting themanual means with said apparatus so as to thereafter applya manual pressure on said wheel brake and subsequently release the 10inder pressure on the wheel brake by thetrapped vacuum.

23. In a device of the character described, manual means for operatingthe same, a wheel brake having a hydraulic motor and means to retractthe same, a hydraulic plunger and cylinder having a force applyingelement acting thereon. constituting means to apply a limited hydraulicpressure on the motor to substantially merely counterbalance the set thebrake, a piston and a cylinder having, operatively connected therewith,a recuperating passage in communication with a liquid reservolr,apparatus adapted to control the application of hydraulic pressure tosaid brake motor from the pressure in said cylinders and acting on saidplunger and piston including operative means hydraulically responsive tothe manual means comprising two liquid check valve faces and seatstherefor adapted to be opened in a direction for flow of the fluidtowards the brake motor and to provide a communication from saidhydraulic plunger cylinder and said piston cylinder respectively to saidreservoir by means of said passage from the brake motor by theretracting means in the normal position of the elements of said deviceand whereby said bydraulically responsive means operatively controls thesequence of the application of the limited hydraulic pressure developedby the plunger and the hydraulic pressure developed by the pistonrespectively to said brake motor for the control and operation of saidbrake.

24. In a device of the character described, manual means for operatingthe same, a hydraulic plunger and cylinder having a spring actingthereon, constituting means to apply a limited hydraulic pressure, awheel brake having a hydraulic motor and means to retract the same. apiston and a cylinder having, operative; connected therewith, arecuperating passage in communication with a liquid reservoir includingmeans controlled by the movement of the piston to open the said passagein the initial position thereof, apparatus adapted to control theapplication of hydraulic pressure to said brake motor from the pressurein said cylinders and acting on said plunger and piston includingoperative means hydraulically responsive to the manual means wherebyliquid is returned to said reservoir from the brake motor by theretracting means in the normal position of the elements retracting meansto l of said device and whereby said hydraulically responsive meansoperativeiy controls the sequence of the application of the limitedpressure and the pressure developed by the manual means respectively tosaid brake motor for the control and operation of said brake.

25. In a device of the character described, manual means for operatingthe same, a wheel brake having a hydraulic motor and means to retractthe same, a hydraulic plunger and cylhaving a power operated deviceacting thereon, constituting means to apply a limited hydraulic pressureon the motor to substantially merely colmter-balance the retractingmeans to set the brake. a piston and a cylinder having, operativelyconnected therewith, a recuperating passage in communication with aliquid reservoir, apparatus adapted to control the application ofhydraulic pressure to said brake motor means hydraulically responsive tothe manual means comprising two liquid check valve faces and seatstherefor adapted to be opened in a direction for flow of the fluidtowards the brake motor and to provide a communication from saidhydraulic plunger cylinder and said piston cylinder respectively to saidreservoir by means of said passage from the brake motor by theretracting means in the normal position of the elements of said deviceand whereby said hydraulically responsive means operatively. controlsthe sequence of the application of the limited hydraulic pressuredeveloped by the plunger and the hydraulic pressure developed by thepiston respectively to said brake motor for the control and operation ofsaid brake.

26. In a device of the character described, manual means for operatingthe same, a wheel brake having a hydraulic motor and means to retractthe same, a hydraulic plunger and cyllnder having a force applyingelement acting thereon, constituting means to apply a limited hydraulicpressure on the motor to substantially merely counter-balance theretracting means to set the brake, a piston and a cylinder having,operatively connected therewith, a recuperating passage in communicationwith a liquid reservoir, apparatus adapted to control the application ofhydraulic pressure to said brake motor from the pressure in saidcylinders and acting on said plunger and piston including operativemeans having a valve device cooperating therewith hydraulicallyresponsive to the manual means comprising two liquid check valve facesand seats therefor adapted to be opened in a direction for flow oi thefluid towards the brake motor and to provide a communication from saidhydraulic plunger cylinder and said piston cylinder respectively to saidreservoir by means of said passage from-the brake motor by theretracting means in the normal position of the elements of said deviceand whereby said hydraulically responsive means operatively controls thesequence of the application of the limited hydraulic pressure developedby the plunger and the hydraulic pressure developed by the pistonrespectively to said brake motor for the control and operation of saidbrake.

27. In a device of the character described, manual means for operatingthe same, a wheel brake having a hydraulic motor and means to retractthe same, a hydraulic plunger and cylinder having a force applyingelement acting thereon, constituting means to apply a limited hydraulicpressure on the motor to substantially merely counter-balance theretracting means to set the brake, a piston and a cylinder having,operatlvely connected therewith, a recuperating passage in communicationwith a liquid reservoir, apparatus adapted to control the application ofhydraulic pressure to said brake motor from the pressure in saidcylinders and acting on said plunger and piston including operativemeans having a lost motion and valve device cooperating therewithhydraulically responsive to the manual means comprising two liquid checkvalve laces and seats therefor adapted to be opened in a direction forhow of the fluid towards the brake motor and to provide a communicationfrom said hydraulic plunger cylinder and said piston cylinderrespectively to said reservoir by means of said passage from the brakemotor by the retracting means in the normal position of the elements ofsaid device and whereby said hydraulically responsive means operativelycontrols the sequence of the application oi the limited hydraulicpressure developed by the plunger and the hydraulic pressure developedby the piston respectively to said brake motor for the control andoperation of said brake.

28. In a device of the character described, manual means for operatingthe same, including a treadle with a short range of travel, a wheelbrake having a hydraulic motor andmeans to retract the same, a hydraulicplunger and cylinder having a power operated device acting thereon,constituting means to apply a limited hydraulic pressure on the motor,to substantially merely counterbalance the retracting means 'to set thebrakes, a piston and a cylinder having, operatively connected therewith,a recuperating passage in communication with a liquid reservoir,apparatus adapted tocontrol the application of hydraulic pressure tosaid brake motor from the pressure in said cylinders and acting on saidplunger and piston including operative means hydraulically responsive tothe manual means comprising two liquid check valve faces and seatstherefor adapted to be opened in a direction for flow of the fluidtowards the brake motor and to provide a communication from saidhydraulic plunger cylinder and said piston cylinder respectively to saidreservoir by means of said passage from the brake motor by theretracting means in the normal position of the elements of said deviceand whereby said hydraulically responsive means operatively controls thesequence of the application of the limited hydraulic pressure developedby the plunger and the hydraulic pressure developed by the pistonrespectively to said brake motor for the control and operation of saidbrake.

29. In a device of the character described, manual means for operatingthe same, a wheel brake having a power operated hydraulic motor andmeans to retract the same, a hydraulic plunger and cylinder having apower operated device acting thereon. constituting means to apply alimited hydraulic pressure on the motor, to substantially merelycounterbalance the retracting means to set the brakes, a piston and acylinder of reduced capacity having, operatively connected therewith, arecuperating passage in communication with a liquid reservoir, apparatusadapted to control the application of hydraulic pressure to said brakemotor; from the pressure in said cylinders and acting on said plungerand piston including operative means hydraulically responsive to themanual means comprising two liquid check valve faces and seats thereforadapted to be opened in a direction for flow of the fluid towards thebrake motor and to provide a communication from said hydraulic plungercylinder and said piston cylinder respectively to said reservoir bymeans of said passage from the brake motor by the retracting means inthe normal position of the elements or said device and whereby saidhydraulically responsive means operatively controls the sequence of theapplication of the limited hydraulic pressure developed by the plungerand the hydraulic pressure developed by the piston respectively to saidbrake motor for the control and operation of said brake.

30. In a device of the character described, a source of vacuum, a vacuumvalve associated therewith, a wheel brake, manual operating means havinga connection to operate said valve, apparatus, including a spring and amovable wall associated with said spring, adapted to apply said vacuumto release spring pressure while the vacuum is being applied to bothsides of said wall, said apparatus constituting means to substantiallymerely set the brake, and means connecting the manual means with saidapparatus so as to thereafter have effective a manual pressure on saidwheel brake.

31. In a device of the character described, a source of vacuum, a checkvalve to trap the vacuum received by the device therefrom, a vacuumvalve associated therewith, a wheel brake, manual operating means havinga connection to operate said valve, apparatus including a spring,adapted to apply said vacuum to release spring pressure while the vacuumtrapped by said check valve is being applied, said apparatusconstituting means to substantially merely set the brake, and meansconnecting the manual means with said apparatus soas to thereafter haveeffective a manual pressure on said wheel brake and subsequently releasethe pressure on the wheel brake by the trapped vacuum.

EDWARD A. ROCKWELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,899,009 Bradbury Feb. 28, 19332,078,209 Sanford et a1. Apr. 20, 1937 2,106,757 Oliver Feb. 1, 19382,106,758 Oliver Feb. 1, 1938 2,112,609 Bchnell Mar. 29, 1938 2,260,492Stelzer Oct. 28, 1941 Certificate of Correction Reissue No. 23,081.January 25, 1949. EDWARD A. ROCKWELL It is hereby certified that errorsappear in the printed specification of the above numbered patentrequiring correction as follows:

Column 11, line 36, claim 28, and column 12, line 1, claim 29, for theword "brekes read brake;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 24th day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

